The U.S. State Department is being tight-lipped on the whereabouts of blind Chinese dissident Chen Guangcheng, who escaped house arrest last week, but the organization that helped him escape says he's in the hands of U.S. diplomats.

Chen, a 40-year-old human rights activist who has campaigned for disabled rights and against forced abortions, scaled a wall and slipped past around 100 security guards surrounding his house.

Bob Fu, the founder and president of ChinaAid, which aided Chen in his getaway, called the escape an "extraordinary adventure."

"He walked for hours from his own home in the middle of the night. He was wounded, wet, covered in mud. He swam across a river," Fu told ABC News.

Chen was picked up by supporters and driven to Beijing on April 23. Several friends hid him in different locations until his last host was able to reach out to the U.S. Embassy in Beijing on April 27, Fu said.

"He's now 100 percent safe. He's still in China, inside some diplomatic building in the hands of U.S. diplomats," Fu said.

Fu said he is not able to discuss the details of Chen's whereabouts because negotiations are still in progress, but it is widely believed that he is in U.S. custody.

"Very high level diplomatic discussion between China and the U.S. is now in progress," Fu said.

If Chen is in U.S. custody, this would be the first time since 1989, when the United States took in student supporter Fang Lizhi during the Tiananmen Square protests, that the United States has taken in a human rights activist.

At a State Department briefing Friday, spokeswoman Victoria Nuland would not comment on the situation other than to say the United States has called for Chen's release in the past.

"As you know, we have spoken out about his case in the past," Nuland said.

Fu said the Chinese government is deliberating and will probably release a formal response today or Monday.

"My gut feeling is that the government wants to get rid of him, because he is a potential continual troublemaker in their eyes," Fu said. "He would prefer to remain in China. We offered him an underground railroad to reach a Western nation, but he was not willing to take that route. His own words are that he will fight to the end. He wants to live a normal Chinese citizen's life."

But if the Chinese government will not guarantee his freedom and safety, then Chen has no other option but to leave, said Fu.

Chen was imprisoned for four years and three months after filing a lawsuit against the Shandong Province government on behalf of women who were forced to undergo abortions and sterilizations. Upon his release in 2010, Chen was put under house arrest. For the last 20 months, Chen's house was surrounded by guards who would not allow anyone to come near. Officials installed surveillance cameras and a phone jamming device in an effort to prevent Chen from communicating with the outside world.

While he was hiding in Beijing, Chen released a video proclaiming his escape. In the video, he states three requests to Chinese Premier Wen Jiabao: that corrupt officials are held accountable, that his family is protected, and that local government officials who persecuted him and his family are investigated and punished for their actions.

In the video, Chen gave graphic details of government abuses against his family, including that his 80-year-old mother was beaten on her birthday, and his wife's eye socket was broken but she was not allowed to seek medical treatment.

Word of the escape came only days before Secretary of State Hilary Clinton, Treasury Secretary Timothy Geitner and Federal Reserve Chairman Ben Bernake are scheduled to be in Beijing for the Strategic and Economic Dialogues.

Kurt Campbell, the Assistant Secretary of State for East Asian and Pacific Affairs, arrived in Beijing today ahead of schedule.

"It could become [a major international incident] if it is mishandled. Again, we will have to see how the Chinese handle it," said Kenneth Lieberthal, director of the China Center and a senior fellow at the Brookings Institution.